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XRT7250 Datasheet, PDF (204/463 Pages) Exar Corporation – DS3/E3 FRAMER IC
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DS3/E3 FRAMER IC
XRT7250
REV. 1.1.1
FIGURE 75. ILLUSTRATION ON HOW THE RECEIVE DS3 FRAMER (WITHIN THE XRT7250 FRAMER IC) BEING INTER-
FACE TO THEXRT7300 LINE INTERFACE UNIT, WHILE THE FRAMER IS OPERATING IN BIPOLAR MODE
TxSER
TxInClk
TxFrame
NIBBLEINTF
RESETB
INTB
CSB
RW
DS
AS
INTB
A[8:0]
D[7:0]
5V
RxSer
RxClk
RxFrame
RxLOS
RxOOF
RxRED
RxAIS
U1
46
43
61
TxSER
TxInClk
TxFrame
25 NIBBLEINTF
28 RESETB
13
8
7
10
9
6
INTB
CSB
WRB_RW
RDB_DS
ALE_AS
Rdy_Dtck
15
16
17
18
19
20
21
22
23
A0
A1
A2
A3
A4
A5
A6
A7
A8
32
33
34
35
36
37
38
D0
D1
D2
D3
D4
D5
39 D6
D7
27 MOTO
86
88
90
RxSer
RxClk
RxFrame
95
94
93
87
RxLOS
RxOOF
RxRED
RxAIS
XRT7250
65
TxPOS
TxNEG 64
TxLineClk 63
DMO 79
ExtLOS 78
RLOL 77
LLOOP 69
RLOOP 70
TAOS 68
TxLEV 67
ENCODIS 66
REQB 71
RxPOS 76
RxNEG 75
RxLineClk 74
U2
37
TPDATA
38 TNDATA
36 TCLK
4 DMO
24 RLOS
23 RLOL
14 LLB
15 RLB
2 TAOS
1 TxLEV
21 ENCODIS
12 REQDIS
33 RPOS
32 RNEG
31 RCLK1
XRT7300
41
TTIP
TRING 40
MTIP 44
MRING 43
1 R3 2
270
1 R4 2
270
R1
1
2
36
1 T1 5
R2
1
2
36
4
8
1:1
TTIP
TRING
8
RTIP
RRING 9
C1
12
0.01uF
R5
37.5
R6
37.5
1 T2 5
4
8
1:1
RTIP
RRING
4.3.1.2.1 AMI Decoding
AMI or Alternate Mark Inversion, means that consec-
utive one's pulses (or marks) will be of opposite polar-
ity with respect to each other. This line code involves
the use of three different amplitude levels: +1, 0, and -
1. The +1 and -1 amplitude signals are used to repre-
sent one's (or mark) pulses and the "0" amplitude
pulses (or the absence of a pulse) are used to repre-
sent zeros (or space) pulses. The general rule for the
AMI line code is: if a given mark pulse is of positive
polarity, then the very next mark pulse will be of nega-
tive polarity and vice versa. This alternating-polarity
relationship exists between two consecutive mark
pulses, independent of the number of zeros that exist
between these two pulses. Figure 76 presents an il-
lustration of the AMI Line Code as would appear at
the RxPOS and RxNEG input pins of the Framer, as
well as the corresponding output signal on the line.
FIGURE 76. ILLUSTRATION OF AMI LINE CODE
Data 1 0 1 1 0 0 0 1 0 1 1 1 1 0 1 1 0 1 1 0 0 1 1 0 0 0 0 1
Line Signal
RxPOS
RxNEG
NOTE: One of the reasons that the AMI Line Code has
been chosen for driving copper medium, isolated via trans-
formers, is that this line code has no dc component, thereby
eliminating dc distortion in the line.
4.3.1.2.2 B3ZS Decoding
185
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